1. Field of the Invention
The present invention relates generally to the field of cannulas for laparoscopic examination and surgery, and more specifically to a gasket assembly for sealing around an instrument to prevent loss of air under pressure inside the abdominal cavity, the assembly including a first member with a central internal passageway for receiving instruments, the passageway containing a universal gasket including a cap having a central port and a lip with an inward projecting flange rotatably fit into a groove around the circumference of the first member, the cap having a central hole aligned with the passageway and a first ring with a circumferential exterior groove fit resiliently over the edge of a the central port, a second ring being resiliently fitted into a recess around the passageway entrance, and a latex sleeve fit at one end snugly between the first ring and the cap and at the other end snugly between the second ring and the first member, so that rotating the cap and first ring relative to the second ring stretches the middle portion of the sleeve extending between the rings, the tension in the sleeve in turn causing the middle portion to close radially inward and to make sealing contact with an object extending through the passageway, regardless of the diameter of the object, and rotating the cap in the opposite direction releases the object and opens the passageway.
2. Description of the Prior Art
There have long been cannulas for providing laparoscopic access for various procedures. Some of these cannulas have required the use of various reducers to close the space between the cannula walls and each instrument placed within the cannula, to prevent loss of gas from the abdominal cavity. A problem with these reducers is that a different reducer must be used for each instrument having a diameter different from that of the previous instrument. Changing reducers can lead to loss of critical time and carries the risk that the proper reducer may be missing at a crucial moment.
Berry, et al., U.S. Pat. No. 5,158,553, issued on Oct. 27, 1992, discloses a rotatably actuated constricting catheter valve. Berry includes a hub which is joined to the catheter, and a rotatable cap which is joined to the hub. An elastomeric sleeve is positioned in an opening through the interior of the valve body. One end of the elastomeric sleeve is joined to the rotatable cap and the other end is joined to the hub, so that turning the cap collapses the sleeve around an instrument within the opening. The Berry sleeve must extend through two annular members, necessarily making the collapsing sleeve portion relatively long. A problem with Berry is that when the Berry members are rotated to close the valve, the elongated sleeve collapses to form essentially a tubular contact surface, gripping the instrument along a wide band. This wide sleeve contact creates a high friction grip which prevents ready axial or rotational movement of the instrument within the opening or passageway. While such movement may not be necessary to the catheter use emphasized in Berry, it is necessary in laparoscopic surgery.
Knepshield, et al., U.S. Pat. No. 4,177,814, issued on Dec. 11, 1979, reveals a self-sealing cannula. Knepshield includes a slotted elastomeric valve positioned in a valve seat with the slot disposed over the passage. The elastomeric valve is compressed to seal the slot, thus sealing the cannula passage around any instrument within the passage. Knepshield includes a thick block or mass of elastic material which has a closed central slit and is compressed in a contracting compartment to create a sealing bulge around an instrument. The problems of Berry et al. are again presented.
It is thus an object of the present invention to provide a universal gasket assembly which can seal around an infinite variety of instrument diameters and thus replaces reducers.
It is another object of the present invention to provide such a gasket assembly which can be readily and securely incorporated into existing laparoscopic cannulas.
It is another object of the present invention to provide such a gasket assembly which uses a short sleeve portion to generate a thin diaphragm gasket, making essentially line contact with an instrument in the assembly, so that instruments can be moved within the assembly with minimal friction resistance
It is still another object of the present invention to provide such a gasket assembly which can simplify and expedite the performance of many laparoscopic procedures.
It is still another object of the present invention to provide a method to make an air-tight connection between the gasket and the cannula.
It is finally an object of the present invention to provide such a gasket assembly which can be inexpensively manufactured from well known, conventional surgical materials.